This invention relates to an air processing apparatus for drying, curing, thermal bonding, cooling, and web transferring permeable or semi-permeable webs such as fabrics, paper, or the like.
Typical of such an apparatus is the honeycomb system described in U.S. Pat. No. 4,542,596. In this system, a non-rotating structure within the roll provides multiple zones for web processing and a vacuum is applied to a plurality of honeycomb grilled conduits so that the web can be dried uniformly and without the ‘blind spots’ which characterize other devices. Unfortunately however, this patented system is flow limited due to the vacuum source and, also, it is limited because air flow through the conduits is not distributed evenly. Moreover, the incorporation of multiple vacuum means within the roll so as to create different zones of air flow on the drying cylinder is difficult to achieve because of the limited space within the cylinder.
The present invention is an improvement over this and other known devices because it allows multiple zones to be created within a cylinder without an internal non-rotating structure; moreover, it allows air to flow equally through the inlet and outlet holes of the conduits so that a web can be dried evenly.
As a result, the present invention makes it possible to isolate and direct air flow into a greater number of separate zones on a single cylinder so that the process air of one zone cannot mix with the process air of another zone.
This ability to selectively isolate and direct air flow into a multiplicity of zones is a feature not shared by the apparatus covered in U.S. Pat. No. 4,542,596 so that now, for the first time, it is possible to obtain economies in energy and other advantages such as isolating contaminants which, heretofore, were impossible to achieve.
These advantages are obtained by incorporating within each cylinder a stationary air distribution tube which distributes process air uniformly throughout the cylinder in an axial direction.
This distribution tube is fixed within the cylinder but it is distinguishable from the non-rotating structure of U.S. Pat. No. 4,542,596 because it revolves as the cylinder revolves and, therefore, is not stationary.
The air which is impelled by the distribution tube within the cylinder ultimately escapes through the outer porous shell through a multiplicity of air zones, a feature which distinguishes this invention from those devices which exhaust the process air from the drying roll in an axial manner.